1. Field of the Invention
The present invention relates to a micropattern measuring method, a micropattern measuring apparatus, and a computer-readable recording medium on which a micropattern measuring program is recorded, in a semiconductor device manufacturing technique.
2. Related Background Art
Generally, a semiconductor device includes plural layers. When a micropattern on the semiconductor device is evaluated using a SEM (Scanning Electron Microscope), for example, in a contact hole pattern or the like after etching, a wiring pattern or the like on a layer thereunder is sometimes seen in an opening thereof.
FIG. 32 and FIG. 33 are diagrams showing examples of a micropattern in a contact hole examined under the SEM. In the case of examination under the SEM, there are various cases where only an edge on one side of a wiring pattern 20 is seen in an opening of a contact hole 10 as shown in FIG. 32, where edges on both sides of the wiring pattern 20 are seen as shown in FIG. 33, and so on due to variations in the wiring size of a lower layer, misalignment, or the like. Moreover, a position or positions where an edge or edges are seen are not fixed.
A common method of measuring the shape of a contact hole is, for example, a method of setting an ROI (region of interest), which is a region to be measured, to cross a central portion of a pattern of a contact hole 30 as shown in FIG. 34, searching for an edge position horizontally outward from a central portion of the ROI, calculating a distance from an edge paired with the extracted edge position, and calculating the maximum width thereof.
In Japanese Patent Laid-open No. Hei 7-27548 (hereinafter referred to as Patent Document 1), a method of designating a center of a contact hole pattern, converting an image to polar coordinates based on the center, and calculating an edge is proposed. In Japanese Patent Laid-open No. 2001-91231 (hereinafter referred to as Patent Document 2), a method of setting a closed region defined by double closed curves along a pattern of a contact hole and searching for an edge of the contact hole in the closed region is proposed.
However, in either method, when the edge of the lower-layer pattern is seen in the opening of the contact hole as shown in FIG. 32 to FIG. 34, the edge of a lower wiring pattern can be within an edge search region. In such a case, the edge of the lower wiring pattern which is situated further inside is extracted, whereby the contact hole cannot be measured accurately.